1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License
*/
package com.android.providers.contacts.aggregation.util;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.android.providers.contacts.ContactsDatabaseHelper.NicknameLookupColumns;
import com.android.providers.contacts.ContactsDatabaseHelper.Tables;
import com.google.android.collect.Maps;
import java.lang.ref.SoftReference;
import java.util.BitSet;
import java.util.HashMap;
/**
* Cache for common nicknames.
*/
public class CommonNicknameCache {
// We will use this much memory (in bits) to optimize the nickname cluster lookup
private static final int NICKNAME_BLOOM_FILTER_SIZE = 0x1FFF; // =long[128]
private BitSet mNicknameBloomFilter;
private HashMap<String, SoftReference<String[]>> mNicknameClusterCache = Maps.newHashMap();
private final SQLiteDatabase mDb;
public CommonNicknameCache(SQLiteDatabase db) {
mDb = db;
}
private final static class NicknameLookupPreloadQuery {
public final static String TABLE = Tables.NICKNAME_LOOKUP;
public final static String[] COLUMNS = new String[] {
NicknameLookupColumns.NAME
};
public final static int NAME = 0;
}
/**
* Read all known common nicknames from the database and populate a Bloom
* filter using the corresponding hash codes. The idea is to eliminate most
* of unnecessary database lookups for nicknames. Given a name, we will take
* its hash code and see if it is set in the Bloom filter. If not, we will know
* that the name is not in the database. If it is, we still need to run a
* query.
* <p>
* Given the size of the filter and the expected size of the nickname table,
* we should expect the combination of the Bloom filter and cache will
* prevent around 98-99% of unnecessary queries from running.
*/
private void preloadNicknameBloomFilter() {
mNicknameBloomFilter = new BitSet(NICKNAME_BLOOM_FILTER_SIZE + 1);
Cursor cursor = mDb.query(NicknameLookupPreloadQuery.TABLE,
NicknameLookupPreloadQuery.COLUMNS,
null, null, null, null, null);
try {
int count = cursor.getCount();
for (int i = 0; i < count; i++) {
cursor.moveToNext();
String normalizedName = cursor.getString(NicknameLookupPreloadQuery.NAME);
int hashCode = normalizedName.hashCode();
mNicknameBloomFilter.set(hashCode & NICKNAME_BLOOM_FILTER_SIZE);
}
} finally {
cursor.close();
}
}
/**
* Returns nickname cluster IDs or null. Maintains cache.
*/
public String[] getCommonNicknameClusters(String normalizedName) {
if (mNicknameBloomFilter == null) {
preloadNicknameBloomFilter();
}
int hashCode = normalizedName.hashCode();
if (!mNicknameBloomFilter.get(hashCode & NICKNAME_BLOOM_FILTER_SIZE)) {
return null;
}
SoftReference<String[]> ref;
String[] clusters = null;
synchronized (mNicknameClusterCache) {
if (mNicknameClusterCache.containsKey(normalizedName)) {
ref = mNicknameClusterCache.get(normalizedName);
if (ref == null) {
return null;
}
clusters = ref.get();
}
}
if (clusters == null) {
clusters = loadNicknameClusters(normalizedName);
ref = clusters == null ? null : new SoftReference<String[]>(clusters);
synchronized (mNicknameClusterCache) {
mNicknameClusterCache.put(normalizedName, ref);
}
}
return clusters;
}
private interface NicknameLookupQuery {
String TABLE = Tables.NICKNAME_LOOKUP;
String[] COLUMNS = new String[] {
NicknameLookupColumns.CLUSTER
};
int CLUSTER = 0;
}
protected String[] loadNicknameClusters(String normalizedName) {
String[] clusters = null;
Cursor cursor = mDb.query(NicknameLookupQuery.TABLE, NicknameLookupQuery.COLUMNS,
NicknameLookupColumns.NAME + "=?", new String[] { normalizedName },
null, null, null);
try {
int count = cursor.getCount();
if (count > 0) {
clusters = new String[count];
for (int i = 0; i < count; i++) {
cursor.moveToNext();
clusters[i] = cursor.getString(NicknameLookupQuery.CLUSTER);
}
}
} finally {
cursor.close();
}
return clusters;
}
}
|
